Write gitception_get in a simpler way
Use gpg --with-colons --print-md
Use gpg --secret-keyring /dev/null where possible
Provide clear messages for signing and verifying
When decrypting or verifying the master key, check input type

We rely on gpg to exit with success, but we also check the status output
to verify that the expected action (decrypt with privkey or verify) was
performed.
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